Sample changers are known in a large number for the most varied applications. Many sample changers have a carousel-like sample rack in which a plurality of positions, preferably equipped with sample vessels, can be triggered automatically. Sample changers with movable sample racks are also known. Sample changers are used for example for sampling, for synthesis, for analysis, etc.
Analysis systems automated with sample changers also often have a provision for connection to an external balance in order to determine the weight of a substance, for example the weight of a sample in automatic analysis devices (e.g. the weight of a titrant in a titration device) which is required for computation of a result. These devices with an external balance are known for example from the companies Mettler, Zymark, Metrohm, etc. Since in these systems the balance is generally not mechanically integrated into the process, considerable manual effort is necessary for example to determine the sample weight. Thus the sample vessel must be taken from the sample changer by hand and placed on the balance, in order to then be placed again by hand on the sample changer after manually weighing-in and taking up the weight. For example, a Zinsser Analytik weighing system is known which conveys the weighing vessel onto the balance and back into the sample rack again using a gripper arm. But the disadvantage in this device is the considerable mechanical effort; the device is accordingly expensive. The disadvantage is adverse effects on operating reliability since the reliability of a gripper arm is usually greatly influenced by the beaker diameter and its tolerance.
Document DE 101 58 179 discloses a sample changer for a comparator balance. The sample changer has a platform on which the sample carrier is mounted. The platform can be moved relative to the balance for delivering the individual units of weighed material onto the sample carriers. When the platform is lowered together with the sample carriers located on it, the ribs of the balance pan penetrate a plurality of recesses of the sample carrier such that a weight which is located on the sample carrier is positioned on the ribs and thus can be weighed. The disadvantage here is the relatively complex mechanism with a platform which can be lowered as a whole. Moreover reaching through the sample carrier by means of the ribs of the balance pan requires high-precision and thus often fault-susceptible mutual positioning and guiding of the balance pan and sample carrier.